THE ENVIRONMENT
waves and its advice on oceanographic matters is often sought by other government departments and the engineering community.
To monitor earthquakes and seismicity, three short-period seismometers are operated at Cheung Chau, High Island and Tsim Bei Tsui. Long-period seismographs at the Observatory's headquarters detect tremors world-wide and information on significant tremors is made public through the media. Strong-motion accelerographs are operated at headquarters and Tate's Cairn. On average, Hong Kong experiences two to three minor earth tremors every year. Seismic data are used by structural engineers in building design, and by local and overseas scientific institutions.
The Hong Kong Time Standard is provided by a caesium beam atomic clock. Accuracy within fractions of a microsecond a day is maintained. A six-pip time signal is sent to Radio Television Hong Kong for broadcast at quarter-hour intervals.
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